As illustrated in FIG. 9, a steering gear for a vehicle is configured to transfer the rotation of a steering wheel 1 to an input axis 3 of a steering gear unit 2, pushes and pulls tie rods 4, 4 which are respectively positioned on the right and left with the rotation of the input axis 3, and then causes a front wheel to have a certain steering angle. The steering wheel 1 is supported by and fixed to a rear end portion of a steering shaft 5. The steering shaft 5 is inserted into a cylindrical steering column 6 in the axial direction and is rotatably supported by the steering column 6. A front end portion of the steering shaft 5 is connected to a rear end portion of an intermediate shaft 8 via a universal joint 7. The front end portion of the intermediate shaft 8 is connected to the input axis 3 via another universal joint 9.
Along with this steering gear, in accordance with the physique and driving posture of a driver, a tilt mechanism which adjusts top and bottom positions of the steering wheel 1, and a telescopic mechanism which adjusts front and rear positions of the steering wheel 1 are widely known. In order to realize the tilt mechanism, the steering column 6 is pivotably supported by a pivot 11 which is provided in the width direction with respect to a vehicle body 10. Here, this width direction is the width direction of the vehicle body 10, and coincides with the lateral direction of the vehicle body 10. A displacement bracket is fixed to a rear portion of the steering column 6. The displacement bracket is displaceably supported with respect to a support bracket 12 which is supported by the vehicle body 10 in the vertical direction and the longitudinal direction. Here, this longitudinal direction is the longitudinal direction of the vehicle body 10. In order to realize the telescopic mechanism that can perform the displacement in the longitudinal direction, the steering column 6 is configured such that an outer column 13 and an inner column 14 are assembled together so as to be telescopically extendable. Further, the steering shaft 5 is configured such that an outer shaft 15 and an inner shaft 16 are assembled together so as to be torque-transferable and extendable through a spline engagement or the like. In an example of FIG. 9, an electric motor 17 is configured as an electric power steering apparatus which reduces power required for an operation of the steering wheel 1, as an auxiliary power unit.
The tilt mechanism and the telescopic mechanism are configured such that, except for a case of being operated electrically, a position of the steering wheel 1 is adjustable and the position after being adjusted can be fixed based on the operation of an adjustment lever. For example, in a first example of the related configuration as illustrated in FIG. 10 and FIG. 11, based on the rotation of an adjustment rod 19 by a adjustment lever 18, an axial dimension of a cam mechanism 20 which is provided at one end portion of the adjustment rod 19 in the axial direction (a left end portion in FIG. 11) is increased and decreased and a cam member 21 is pivotably displaced (for example, refer to Patent Document 1 and Patent Document 2). In the first example of the related configuration, a displacement bracket 22 which is fixed to an outer column 13a is disengaged from a support bracket 12a based on the increase and decrease of the cam mechanism 20. The inner column 14a slides or does not slide into the outer column 13a based on the pivot of the cam member 21.
The adjustment rod 19 is inserted into long holes 24, 24 in the vertical direction which are formed on supporting plate portions 23, 23 on the left and right side of the support bracket 12a, and long holes 25, 25 in the longitudinal direction which are formed in the displacement bracket 22, in the width direction. An outer shaft 15a and an inner shaft 16a configure a steering shaft 5a. In order to adjust the top and bottom positions or the front and rear positions of the steering wheel 1 which is supported by and fixed to the rear end portion of the steering shaft 5a (refer to FIG. 9), the adjustment lever 18 is pivoted in a predetermined direction (typically, in the lower direction), the axial dimension of the cam mechanism 20 is decreased and the cam member 21 is separated from the outer peripheral surface of the inner column 14a. The adjustment rod 19 enables the displacement along with the long holes 24, 24 in the vertical direction, and the rotation around the center axis of the adjustment rod 19. The cam mechanism 20 includes a driving cam 26 and a driven cam 27. The driving cam 26 is supported by and fixed to the one end portion of the adjustment rod 19 in the axial direction in a state where the relative rotation and axial displacement are inhibited (are disabled) with respect to the adjustment rod 19. The driven cam 27 is supported by an intermediate portion of the adjustment rod 19 in the axial direction so as to enable the relative rotation and axial displacement with respect to the adjustment rod 19. A convex portion 28 is provided on an inside surface of the driving cam 26 in the width direction (the right side surface in FIG. 11, and the lower side surface in FIG. 12A and FIG. 12B), and a concave portion 29 and a stepped portion 30 are provided on an outside surface of the driven cam 27 in the width direction (the left side surface in FIG. 11, and the upper side surface in FIG. 12A and FIG. 12B). In order to adjust the top and bottom positions and the front and rear positions of the steering wheel 1, as illustrated in FIG. 12A, by rotating the adjustment lever 18 in a predetermined direction (typically, the lower direction), the convex portion 28 of the driving cam 26 and the concave portion 29 of the driven cam 27 are engaged with each other, and the axial dimension of the cam mechanism 20 is decreased. In this state, the outer column 13a is possibly displaced corresponding to the degree that the adjustment rod 19 can be displaced in the long holes 24, 24 in the vertical direction and the long holes 25, 25 in the longitudinal direction. The steering shaft 5a is rotatably supported in the outer column 13a. That is, the position of the steering wheel 1, which is supported by and fixed to the rear end portion of the steering shaft 5a, can be adjusted. After the steering wheel 1 is moved to a desired position, the adjustment lever 18 is pivoted in a direction opposite to the above-described predetermined direction, and, as illustrated in FIG. 12B, the convex portion 28 of the driving cam 26 and the stepped portion 30 of the driven cam 27 are engaged with each other, and the axial dimension of the cam mechanism 20 is increased. Accordingly, a distance between the driven cam 27 and a nut 31 which is threadedly fixed to a male screw portion 43 provided at the other end portion of the adjustment rod 19 in the axial direction (the right end portion in FIG. 11) is reduced, and thus both of the supporting plate portions 23, 23 firmly press down an outer peripheral surface of the outer column 13a via the displacement bracket 22. At the same time, the cam member 21 presses down an outer peripheral surface of the inner column 14a onto an inner peripheral surface of the outer column 13a. As a result, it is possible to hold the steering wheel 1 at the adjusted position.
In the case of the above-described position adjustment device of the steering wheel, a fitted convex portion 32 which is provided on the outside surface of the driving cam 26 in the width direction is pressed into a fitting hole 33 which is provided in a base end portion of the adjustment lever 18, and thus the driving cam 26 and the adjustment lever 18 are combined without rattling. Further, the one end portion of the adjustment rod 19 in the axial direction is press-fitted (inserted and fixed) into a through hole 34 which is provided in the center portion of the driving cam 26. With such a configuration, the driving cam 26 is supported by the one end portion of the adjustment rod 19 in the axial direction in a state where the relative rotation and axial displacement are inhibited with respect to the adjustment rod 19, and the adjustment lever 18 is supported without rattling with respect to the adjustment rod 19.
The driving cam 26 may be made of sintered metal in order to prevent the abnormal wear or galling from being generated between the driving cam 26 and the driven cam 27. In a case where the driving cam 26 is made of the sintered metal, a fitting portion of the through hole 34 of the driving cam 26 and the adjustment rod 19 is required to have high shape accuracy and dimensional accuracy. As a result, there is a possibility of an increase of the manufacturing cost not only in the driving cam 26 and the adjustment rod 19 but also in the entire position adjustment device of the steering wheel.
On the other hand, FIG. 13 illustrates a second example of the related configuration relating to the position adjustment apparatus of the steering wheel. In the case of the second example in the related configuration, a sleeve 35 made of carbon steel, which is made of a synthetic resin such as a polyamide resin, a light alloy such as an aluminum-based alloy, or carbon steel such as S45C, is inserted into the through hole 34a of the driving cam 26a of the cam mechanism 20 (refer to FIG. 11), and then the adjustment rod 19 is inserted into (loosely fitted to) the internal diameter of the sleeve 35. Accordingly, the driving cam 26a is supported by the one end portion of the adjustment rod 19 in the axial direction so as to enable the relative rotation and axial displacement with respect to the adjustment rod 19. The driven cam (not shown) is supported by the intermediate portion of the adjustment rod 19 in the axial direction so as to be displaceable in the axial direction with respect to the adjustment rod 19, and inhibits the relative rotation thereof.
In the second example as described above, the engagement portion between the driving cam 26a and the sleeve 35 does not require particularly high shape accuracy and dimensional accuracy. For this reason, even in a case where the driving cam 26a is made of the sintered metal, the manufacturing cost of the position adjustment device of the steering wheel is not excessively increased. However, there is a possibility of the following problems. That is, there is an annular gap between the inner peripheral surface of the sleeve 35 and the outer peripheral surface of the adjustment rod 19. Even in this case, in a state where the axial dimension of the cam mechanism 20 (refer to FIG. 11) is increased, the driving cam 26a is firmly sandwiched between the driven cam and a nut 38 (refer to FIG. 11) which is threadedly fixed to the one end portion of the adjustment rod 19 in the axial direction, and thus the rattling of the driving cam 26a with respect to the adjustment rod 19 is suppressed. However, in a state where the adjustment lever 18 is rotated in a predetermined direction, and the axial dimension of the cam mechanism 20 is decreased, there is a possibility of the rattling of the driving cam 26a and the adjustment lever 18 with respect to the adjustment rod 19 (in the radial direction and the axial direction).